The invention relates to a picture-taking lens for an aerial mapping camera.
In objectives for aerial photographic technology, the surface weighted resolution capability (AWAR), the resolution at the worst picture site, distortion and lateral chromatic aberrations are the main characteristic performance data that are used to describe the optical imaging performance. They must be considered in relation to the technological degree of difficulty of making the lens, to the material used and to the mass and dimensions of the objective. At the present time, there are three picture-taking lenses of comparable quality for aerial mapping cameras:
The universal Aviogon 15/4 UAg (f:4), with an AWAR of 75 L/mm, a resolution of 40 L/mm at the worst picture site and a distortion of .+-.3 microns measured at the overall length of 372 mm and the maximum lens diameter of about 234 mm. The lens has a 13-lens objective construction with a 3-fold and a 4-fold wring group, and relatively low performance data. This characteristic performance data for the AWAR and the resolution of the worst site of the picture, moreover are not attained for the full opening of k=4, but only when the aperture is stopped down to 5.6. As a result the maximum opening is practically not usable if the highest possible resolution is required. For this objective, approximately 550 nm has been selected as the achromatization wavelength. As a result, the lateral chromatic aberration in the short wave region for 480 nm is less than 20 microns. In the longwave range of the spectrum, lateral chromatic aberrations of up to 20 microns occur at 650 nm because of the relatively large secondary spectrum.
The Pleogon A 4/150 has an AWAR of 80 L/mm, a resolution of 67 L/mm at the worst site of the picture and a distortion of .+-.5 microns. Moreover, it is known that the best examples of this type achieve an AWAR of up to 96 L/mm and a distortion of .+-.1 micron. For the achromitization of the lateral chromatic aberration, a wavelength of 610 nm was selected. Because of the relatively large secondary spectrum, a lateral chromatic aberration of about 60 microns remains for a wave length of 480 nm and a lateral chromatic aberration of about 5 microns remains for a wave length of 650 nm. Nothing is known of the mass and dimensions of the objective. The material outlay with 9 lenses is relative low. However, the lenses of the objective have an extreme shape, with an center thickness ratio of about 30:1 and extreme deflections. The objective is therefore difficult technologically to produce.
The Lamegon 4.5/150 DM has an AWAR of 90 L/mm, a resolution of 70 L mm at the worst site of the picture and a distortion of .+-.1 microns. With this objective, however, the lateral chromatic aberration limits the performance in optical representation. For 470 nm, based on the wavelength of 640 nm at which the achromatization lies, it amounts to 30 microns. In the longwave region of the spectrum of 768 nm the lateral chromatic aberration is 30 microns. The relative large secondary spectrum of all known technical solutions does not ensure that the distortion is independent of the spectral sensitivity of the film. In color photographs, it necessarily leads to clearly identifiable color fringes and disadvantageously affects the resolution capability of broad-band sensitized black-and-white films. The AWAR achieved and the resolution capability at the worst site of the picture do not satisfy the highest requirements of photogrammetric recording techniques.